Going back to the opening post, the basic Aristocratic Roman domus (as distinguished from the an apartment house of Rome or Ostia, or the rural bungalo) began as an entryway leading to an atrium with rooms grouped around it. Later, onto that first section a rear section was added and rooms grouped around a peristylum.
"Simple Domus Floor Plan" (SHOWN FOR ILLUSTRATION PURPOSES)
The first section was Italian, and the names were Latin: The vestibulum, fauces, atrium, alae, tablinum, taberba, hortus. The rear or additional section, Greek in origin and design, had names which were Greek: the peristylum, triclinium, oecus, exhedra, (and then the aforementioned Italian (Latin named) hortus).
Interestingly the connecting passage between the two sections (atrium to perstyle) was called the andron(es) where a confusion occurs, is a misuse or misapplication of the Greek word. As Vitruvius says: "Between the peristylium and the lodging rooms are passages, which are called Mesaul